The present invention pertains to instruments for fixating the eye during ocular surgery such as cataract extraction by the small incision technique, commonly known as Phacoemulsification or Phaco technique and other operations of the anterior segment of the eye that are performed under local anesthesia.
In recent years, two surgical techniques for removing a cataract from the eye are employed. The large incision technique and the small incision or Phaco technique.
In the large incision technique, an incision (approximately 8-10 mm), almost half of the circumference of the cornea is made, and the cataract is expressed or squeezed out of the eye manually. The advantage with this technique is that it is much easier to perform. The disadvantages are the longer time to recuperate, and it produces more astigmatism.
In the small incision or Phaco technique, a small incision, approximately three (3) mm long is made on the peripheral margin of the cornea (usually temporal). Then a needle or sharp forceps is used to puncture the anterior lens capsule and tear a circular opening (capsulorhexis) to create access to the cataractous lens cortex and nucleus through the corneal incision and capsular opening. An ultrasonic cutting tip is then inserted inside the eye to remove the cataract. The advantages with this technique are the stronger wound, faster recuperation, and less astigmatism.
Ophthalmologists have continued to improve the Phaco technique. One such improvement is the recent change from needle-block anesthesia injections which paralyze the eye to a topical anesthesia, administered through eye drops. The eye drops eliminate the swelling, bruising, discomfort and trauma to the tissues around the eye which are often associated with needle-block anesthesia injections and further eliminates the possible complication of inadvertent ocular perforation from the anesthetic needle.
While the topical anesthesia has many beneficial aspects, including freedom of movement immediately after the completion of the Phaco procedure, it also allows the undesirable free movement of the eye during the surgical procedure.
Ophthalmologists have often used three different approaches to fixate the eye under such circumstances. One has been to use a toothed ring that extends around the perimeter of the cornea which is pressed down into the sclera. Another approach has been to use forceps to grab the outside of the eye to restrict movement. Alternatively, it is possible to use a special diamond knife to hold the eye steady after one of the two incisions is made.
While these approaches have been used in the past, each has serious drawbacks. The toothed ring requires an increased pressure in the eye when the surgeon presses the ring into the sclera. During the part of the operation where the anterior capsule is tom open (capsulorhexis), the increased intraocular pressure makes the procedure more difficult and increases the likelihood of a complication. The approach using forceps to restrain eye movement has the drawback that the forceps on occasion accidentally release the eye because it is difficult to grasp the eye firmly, or in other situations, tear blood vessels and cause bleeding.
Using the knife to hold the eye prevents movement in three directions (to either side or toward the handle), but not in the fourth direction--toward the point of the knife. The two other drawbacks of the diamond knife are the expense of the instrument and the difficulty of reinsertion after removal. It is difficult to reinsert the blade in the same incision without creating a new cut.
Consequently, there is a need for improvement in instruments and methods for fixating the eye during cataract surgery.